Attaching Wood To Concrete

!±8± Attaching Wood To Concrete

A very important tip is to use the right tool for each method. When you're dealing with concrete and masonry, you're obviously dealing with extremely hard material. Woodworking hammers are too light and steel drill bits too soft. The concrete is also brittle. Hard sharp chips are likely to fly out as you work on it, so always wear safety goggles to protect your eyes.

Nails. Nailing wood directly to concrete is probably the simplest, quickest and cheapest method. Unfortunately, once driven, these nails may jar loose from a few hammer blows to the side of the board. So, they are better for temporary fastening.

You'll usually find two types of special nails at the hardware store, cut nails and hardened concrete nails. Drive nails with a 2- to 4-lb. hammer. Actually, it's very hard to drive nails into cured (hardened) concrete, even with a 4-lb. hammer. They work best in concrete that's only cured for a few days.

Nails can be quite effective in mortar joints, however. Mortar is softer than either the concrete block or brick, and it holds nails fairly well. For best results, drive them right along the joint edge. And here's a professional tip: for improved holding power, run a bead of glue along the backside of your wood before nailing it up.

Predrilled Fasteners. There is a family of fasteners that can be driven into a predrilled hole. These not only fasten wood to concrete, but will fasten just about anything else to concrete as well.

They install easily, simply drill through the wood and into the concrete and drive the fastener.

Drilling the hole is the only difficult part. Use a carbide tip bit. Because these holes are relatively small, your standard 1/4-inch or 3/8 inch power drill can do an adequate job, although each hole may take several minutes to bore. A hammer drill, however, will drill your hole in a matter of seconds. A hammer drill is expensive, but they can be rented. If you have a lot of holes to drill, they'll save a lot of time.

It's a good idea to glue your wood to the concrete or masonry with this system as well, especially when using screws. Once screws are jarred loose, they may not retighten.

Expansion Fasteners. These fasteners are simple, effective and can carry a heavy load. They may be retightened should they be jarred loose.

Because they require a larger hole, you really need a hammer drill to bore the concrete. If you can't buy, borrow or rent one, try boring a 1/8 inch hole first with a carbide bit. Then use progressively larger carbide bits until you reach the proper size.

Buy these fasteners long enough to wedge into the concrete as deep as the wood is thick. Drill your hole an extra 1/4 inch deep, since the bolt draws back slightly when tightened.

Power Fasteners. These are extremely fast, powerful and dangerous. They are primarily professional tools which any untrained homeowner should steer clear of until they fully understanding the safety precautions. With power fasteners you can quickly nail into just about any concrete or masonry surface. Both the air and the power-actuated systems drive hardened nails through the wood and solidly into the concrete in one shot. Flying metal, wood or concrete are certain hazards, so eye protection is essential.

Glue. Over the past ten years construction adhesives have improved and become more specialized. You can securely glue just about anything to a wall now. Since glued wood must be held tightly in place until the glue sets, it's handy to use an adhesive with another fastening system for mutual reinforcement; the glue dampens the vibration and jarring that may weaken the fasteners, and the fasteners hold the wood tightly until the glue sets.

Proper preparation ensures a good glue bond. Be sure the wood and the concrete surfaces are clean and dry. Loose paint, surface chalking or moisture will cause the bond to release. When working with a very rough surface, apply a generous bead to bridge the wider gaps between the wood and concrete.